Dandruff or pityriasis capitis is the most widespread and under-diagnosed scalp problem worldwide. It will affect about half of Caucasians to some degree before they reach 20 years old.
It is characterized by discarded stratum corneum clumped into oily white flakes. In normal scalp, skin migration is about 28 days and cells shed as single cells, while in scalps with dandruff, cell migration is of about 7 to 21 days and cells shed in clumps of about 100-1000 cells. Although the precise link between the Malassezia fungus and dandruff is unclear, it is recognized that this fungus contributes to dandruff as follows: Malassezia which requires fat to grow, uses different types of lipase to hydrolyze triglycerides on the scalp surface (e.g., on comeocytes), the hydrolysis releases unsaturated fatty acid which in turn increases Malassezia growth and may cause inflammation and itching. Malassezia represents about 46% of the microflora in normal subjects, and about 74% of the microflora in subjects with dandruff. The species Malassezia globosa and restricta are reported to be the dominant species present in the human scalp, with M. globosa being the species with the highest lipase activity. Malassezia's presence alone is reported not be sufficient to cause dandruff, however.
Other contributing factors include genetic predisposition, androgenetic metabolism (i.e., hormonal change), psychological stress, environmental irritants (pollution, high humidity, temperature, UV radiation) and cosmetics.
Current anti-dandruff ingredients attempt to control lipase activity, sebum, fungus or inflammation, and/or include keratolytic, anti-microbial/anti-fungal, or anti-proliferative agents. Keratolitic agents (e.g., salicylic acid (Sebex™, Sebulex™, Neutrogena™ T/Sal)) will remove a considerable proportion of flakes in patients with milder conditions. The majority of commercially available dandruff treatments include anti-microbial/anti-fungal agents, which have been shown to improve the visible symptom of flaking and restore the underlying skin condition (Warner et al., 2001). For example, these agents include pyrithione zinc (Selsun Blue™ for Itchy Dry Scalp, Neutrogena™ T/Gel Daily Control Dandruff Shampoo, Head & Shoulders™), selenium sulfide (Dandrex™, Head & Shoulders™ Clinical Strength, Selsun™), ketoconazole (Extina™, Nizoral™ A-D, Xolegel™), and ciclopirox. Anti-proliferative agents (e.g., coal tar (Denorex Therapeutic Protection™, Neutrogena™ T/Gel, Scytera™)) decrease epidermal proliferation and dermal infiltrates (Schwartz et al., 2004). Adjunctive treatment with topical steroids may also be helpful in patients whose condition includes evidence of an inflammatory component. Given that many subjects with dandruff may require regular, long-term use of therapeutic agents, it is important that the treatments be formulated so as to be aesthetically and cosmetically acceptable to the patient.
There are a number of potential disadvantages associated with current dandruff treatments. For example, while coal tar works as both an anti-dandruff agent and a biocide, it is a known carcinogen that may be toxic to the skin's health. In fact, the Environmental Working Group's cosmetic safety database ranks it a 10 on a scale of 0 to 10, with 10 being the most hazardous to health. Accordingly, coal tar is banned in various geographic regions such as Canada and the European Union, although it is available in over-the-counter shampoos in the United States. Some people may be allergic to zinc pyrithione, or may experience skin irritation caused by this ingredient, although both of these side effects are very rare, according to Drug Information Online. Zinc pyrithione may also irritate eyes on contact and can cause nausea if swallowed, according to the National Library of Medicine's Households Products Database. Salicylic acid may help with dandruff by loosening dead skin crusts. However, a stinging or burning sensation may be experienced when applying a shampoo containing the acid, and it may irritate skin, according to the National Institutes of Health. More serious, potential side effects may include vomiting, dizziness and changes in breathing rates, though such effects are rare. Some people may be allergic to selenium according to the National Institutes of Health (NIH). The NIH also reports that skin irritation, rashes and other topical side effects are most often associated with shampoos containing selenium at a strength of 2.5 percent or higher. Ketoconazole may prompt itching of skin, hives and a rash when using topically, according to the NIH. More serious side effects, such as an increased risk of cancer, are related to internal ingestion of the chemical.
Although the above mentioned chemicals have been reported to show some efficacy, it may be advantageous to reduce their concentration in an anti-dandruff treatment (e.g., by combining them with other active ingredients) to decrease the risk of triggering their potential side effects. Furthermore, due to health and environmental concerns, as well as increasing pressure from consumers, naturally-derived and/or eco-friendly anti-dandruff active ingredients would be highly desirable.
The present description refers to a number of documents, the content of which is herein incorporated by reference in their entirety.